Methadone dose conversions

Deaths, cardiac and resp have been reported during initiation and conversion of pain pts to methadone Tx from Tx w/ other opioids Uses Severe pain detox w/ maint of narcotic addiction Action Narcotic analgesic Dose Adults. 2.5-10 mg IM q3-8h or 5-15 mg PO q8h titrate as needed Feds. 0.7 mg/kg/24 h PO or IM -s- q8h T slowly to avoid resp depression X in renal impair Caution [B/D (prolonged use/high doses at term), + (w/ doses =/> 20 mg/24 h)], severe liver Dz Disp Tabs, inj SE Resp depression, sedation, constipation, urinary retention, T QT interval, arrhythmias Interactions T Effects W/ cimetidine, CNS depressants, protease inhibitors EtOH T effects OF anticoagulants, antihistamines, barbiturates, glutethimide, methocarbamol ... 

Individuals who have been misusing pharmaceutical opioids pose a particular problem, as any straight conversion from claimed average usage tends to result in methadone dosages which appear excessively high. In practice, such users can usually be given doses of... 

Allopurinol increases didanosine plasma concentrations and their coadministration is not recommended. Ganciclovir, tenofovir and disoproxil also increase didanosine plasma concentrations, and dose reduction is recommended. Conversely, methadone decreases didanosine plasma concentrations, and appropriate doses for the combination have not been established. Didanosine should not be administered with drugs that cause pancreatic or neurotoxicity. Ribavirin increases its risk of toxicity and should not be coadministered. 

The role of opioid rotation in cancer pain management has been described, highlighting the limitations of equianalgesic tablets and the need for monitoring and individualization of dose. This is particularly important when methadone is used as the opioid for conversion. The authors referred to a greater than expected potency of methadone, with excessive sedation and opioid-related adverse effects, if the switch is done on a one-to-one basis. They suggested that the calculated equianalgesic dose of methadone should be reduced by 75-90% and the dose then titrated upwards if necessary (47,48). 

Administration (FDA) for the treatment of opioid addiction. Treatment is initiated with buprenorphine alone administered sublingually, followed by maintenance therapy with a combination of buprenorphine and naloxone (Suboxone) to minimize abuse potential. The partial agonist properties of buprenorphine limit its usefulness for the treatment of addicts who require high maintenance doses of opioids. However, conversion to maintenance treatment with higher doses of methadone, a full agonist, is possible. 

CODEINE In contrast to morphine, codeine is -60% as effective orally as parenteraUy as an analgesic and as a respiratory depressant. Codeine analogs such as levorphanol, oxycodone, and methadone have a high ratio of oral-to-parenteral potency. The greater oral efficacy of these drugs reflects lower first-pass metabolism. Once absorbed, codeine is metaboUzed by the liver, and its metabolites are excreted chiefly as inactive forms in the urine. A relatively small fraction (-10%) of administered codeine is O-demethylated to morphine, and free and conjugated morphine can be found in the urine after therapeutic doses of codeine. Codeine has an exceptionally low affinity for opioid receptors, and the analgesic effect of codeine is due to its conversion to morphine. However, its antitussive actions may involve distinct receptors that bind codeine itself. The tj of codeine in plasma is 2-4 hours. 

In opioid-tolerant patients, no single ratio is suitable for converting a specific dose of morphine into an equivalent dose of methadone and the conversion to methadone should be performed cautiously. 

Daily chronic oral Conversion ratio oral morphine dose morphine to oral methadone... 

Many opioid conversion charts misrepresent the 130 equipotency ratios of morphine to methadone, as they extrapolate a single-dose effect and are not appli-... 

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